What the Guard House is
The National Astronomical Observatory Guard House, built in 1924 just north of the main gate in Osawa, Mitaka City, Tokyo, is a single-storey timber building of 66 square metres that became a Registered Tangible Cultural Property in 2014. Its roof is covered in sheet metal.
Of the ten registered structures on the campus, this is the only one made of wood. The rest are concrete, designed as rigid boxes to hold instruments steady. Only the lodge where the gatekeeper sat was built the traditional way.
It now doubles as the visitor reception, so anyone entering the grounds stops here first.
Why it is registered
The National Astronomical Observatory Guard House was listed under the criterion of contributing to the historic character of the landscape, register number 13-0335. The judgement pairs it with the main gate: together they form the composition a visitor meets at the entrance.
For a small ancillary building the detailing is careful. A gabled porch projects from the front, half-timbering appears above the porch and on the gable ends, and the walls are clad in horizontal weatherboard. Someone wanted the institute's front door to look Western.
The year, 1924, is the same as the Gautier Meridian Circle Building. Observing rooms and gate buildings were going up side by side as the observatory settled into Mitaka.
What to look at
The roof is a simple gable entered on the long side, and a second small gabled porch pushes out from it. That two-part arrangement gives depth to a building that covers only 66 square metres.
Look up at the gable end and you will find the pattern of posts and braces of half-timbering. It is applied decoration rather than exposed structure, and together with the weatherboarding it makes the National Astronomical Observatory Guard House resemble a suburban house of the 1920s.
Inside, a central wall once divided the plan into two symmetrical halves, each with a tatami room, of six and four and a half mats, and a lavatory. A Western exterior over tatami floors was a common combination in small government buildings of the period.
Because the building is in use as reception, the unhurried look at the exterior comes after you have signed in.
Visiting
The National Astronomical Observatory Guard House holds the visitor reception desk. The interior is a working office and is not open as an exhibit, though the porch and its joinery are close at hand while you register.
From the visitor route just inside the gate you can see the north gable and the weatherboarded walls. Photography is allowed for private use.
Reception procedure, opening hours and bus access are the same for the whole site and are described on the page for the National Astronomical Observatory of Japan Mitaka Campus.
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Q&A
- What was the National Astronomical Observatory Guard House built for?
- It was built in 1924 as the gatekeeper's lodge, and it now also serves as the visitor reception for the Mitaka campus.
- Can I go inside the National Astronomical Observatory Guard House?
- The interior is a working office and is not open as an exhibit. You will step into the reception area to sign in.
- How is the National Astronomical Observatory Guard House built?
- It is a single-storey timber building with a sheet-metal roof and a floor area of 66 square metres, the only wooden structure among the ten registered entries.
- When did the National Astronomical Observatory Guard House become a cultural property?
- On 25 April 2014, with the register number 13-0335.
- What should I look for at the National Astronomical Observatory Guard House?
- The gabled porch, the half-timbering on the gable ends and the weatherboarded walls. The Western exterior once enclosed tatami rooms.
Basic Information
| Name | National Astronomical Observatory Guard House |
|---|---|
| Location | 2-1007-1 Osawa, Mitaka City, Tokyo |
| Designation | Registered Tangible Cultural Property (building) |
| Year Designated | Registered in 2014 (Heisei 26) |
| Quantity | 1 building |
| Dimensions | Timber, single storey, sheet-metal roof, floor area 66 square metres |
| Owner | Inter-University Research Institute Corporation National Institutes of Natural Sciences |
| Public Access | Exterior only; the interior is in use as reception |
References
- Agency for Cultural Affairs, National Cultural Properties Database: National Astronomical Observatory Guard House
- https://kunishitei.bunka.go.jp/bsys/maindetails/101/00009920
- National Astronomical Observatory of Japan, Mitaka Campus: Visitor Information
- https://www.nao.ac.jp/about-naoj/organization/facilities/mitaka/visit.html
- National Astronomical Observatory of Japan, Mitaka Campus: Facilities Open to Visitors
- https://www.nao.ac.jp/about-naoj/organization/facilities/mitaka/visit-facilities/
Last verified: 2026.09.13
